A scanning laser ophthalmoscope (SLO), which is an ophthalmologic apparatus operable based on the principle of confocal laser microscope, is an apparatus that can perform raster scanning on an eyeground with a laser (i.e., a measuring beam) and can speedily obtain a high-resolution planar image of the eyeground based on the intensity of an optical feedback of the laser. Hereinafter, an apparatus capable of capturing a planar image is referred to as an SLO apparatus.
Further, there is a conventional AO-SLO apparatus including an adaptive optics (AO) system, which performs real-time measurement of an aberration of an eye to be tested with a wavefront sensor and corrects an aberration of a measuring beam or its optical feedback generated at the eye to be tested with a wavefront correction device. The AO-SLO apparatus can acquire a planar image that is excellent in horizontal resolution.
The planar image having excellent horizontal resolution can be used, for example, to extract a retinal blood vessel or a blood cell to observe a blood cell state, or measure the thickness of a nerve fiber bundle to evaluate the disorder of a ganglion cell. Further, the planar image can be used to evaluate visual functions, or measure a density distribution (or alignment) of photoreceptor cells.
A conventional technique capable of obtaining an image of a specific structure, such as organization, cell, or lesion, with an SLO apparatus is discussed in Johnny Tam, et. al., Noninvasive Visualization and analysis of Parafoveal Capillaries in Humans, Investigative Ophthalmology & Visual Science, March 2010, Vol. 51, No. 3, pp 1691-1698. The conventional technique includes setting shooting conditions (e.g., wavelength of signal light) for the SLO apparatus, capturing an image of an area including a macula area, and acquiring an image of a capillary vessel based on the obtained image.
When a single SLO image is obtained by scanning an observation target with signal light having a fixed focus position, the captured image may not include the structure of the observation target. An operator cannot use such a defective image to observe a target structure. Accordingly, the operator is required to change the settings and perform a shooting operation again. Thus, the efficiency of the shooting operation for each tested person deteriorates significantly.